Transparent metal working lubricant composition



Patented Sept. 191, 1961i This invention relates to an aqueoustransparent cutting oil possessing outstanding anti-rust properties andlubricity. More particularly, this invention relates to a cutting oilcomposition which possesses the high heat capacity of water while stillretaining the desirable properties of petroleum base cutting oils.

The use of high machine speeds in metal working operations such ascutting, drilling, broaching, drawing, and the like has placed severedemands on the lubricant employed to cool and lubricate the tool andmetal Work piece. The enormous amount of heat generated at the tool-Workpiece interface must be quickly dissipated in order to prevent damage tothe tool and Work piece. The second major requirement of metal Workinglubricants is the reduction of friction between the tool and work pieceto prevent wear, scoring, and welding of the contacting parts. Therequirements of cooling and lubrieating place severe restrictions on thecomposition of metal working lubricants. Water is an excellent coolingiluid because of its high heat capacity, but it is almost completelydeficient in lubricating properties. Mineral lubricating oils affordexcellent lubrication and reduce friction but are relatively poorcoolants.

A number of metal working lubricants have been formulated to provideboth lubricity and hi h heat capacity. One effective approach has beenthe development of soluble oils, which are mineral oil base lubricantscontaining a substantial concentration of emulsifying agents so thatthey form oil-in-Water emulsions processing both lubricity and goodcooling properties. Another approach is disclosed in U.S. 2,692,859 andinvolves formation of an aqueous, non-corrosive cutting solution. Themetal working composition of this patent comprises water, 0.01 to 10.0weight percent each of an alkyl phenol-ethylene oxide reaction product,an alkali metal nitrite and an inorganic metal phosphate. The alkalimetal nitrite-inorganic metal phosphate combination is alleged to act asa corrosion inhibitor and to improve metal working efiiciency. The alkylphenol-ethylene oxide product acts as a surface active agent. The metalworking lubricant composition of this invention possesses substantialadvantages in cooling, lubricity, low temperature stability andanti-rust properties over both the soluble oil formulations and theaqueous cutting fluid of the afore-identified patent.

The metal working lubricant composition of this invention compriseswater as the main constituent, to 40 percent polyethylene glycol,polypropylene glycol or a mixture thereof, said glycol having an averagemolecular weight between 200 and 800, 3 to 18 percent alkali metalnitrite and 2 to 15 percent of a secondary or tertiary alkanol amine.The lubricating composition of the invention is characterized byoutstanding anti-rust properties, lubricity and excellent lowtemperature stability.

The polyalkylene glycol component of the lubricant composition of theinvention has the following general formula:

wherein R is hydrogen or a methyl radical and n is an integer having avalue of 3 to 18. Polyglycols usable in the formulation of the metalworking lubricants of the invention are the following wherein the numberimmediately following the compound indicates the average molecularWeight:

Polyethylene glycol c 200 Do 300 Do 600 Do 800 Do 500 l olypropyleneglycol 200 Hereafter in the description of the invention the averagemolecular weight of the polyglycol component will be indicated by thenumber immediately succeeding the compound designation.

It is necessary for the polyalkylene glycol component to have an averagemolecular weight between about 200 and 800 in order for the resultinglubricant composition to possess lubricating properties andtransparency. Aqueous compositions containing polyglycols such asdiethylene glycol having a molecular weight below 200 tend to bedeficient in lubricity. At the other end of the scale compositionsprepared with polyethylene or polypropylene glycol having a molecularweight above 800 are hazy and cannot be classified as transparentcutting oils. Polyethylene glycols having average molecular Weightsbetween 400 and 700 are the preferred materials for the formulation ofthe metal working lubricants of the invention.

The concentration of the polyalkylene glycol component is also animportant factor in the production of satisfactory metal Workinglubricants. The polyalkylene glycol constitutes 5 to 40 weight percentof the lubricant with concentrations of 15 to 35 weight percent nor-Ina-11y being employed. lf the concentration of the polyglycol componentis above 40 weight percent of the lubricant composition, an unstableproduct results. For example, a product containing approximately 41percent polyethylene glycol 600, 18.5 percent sodium nitrite and 14.4percent triethanolamine showed substantial crystalline deposits afteronly four days of storage at atmospheric temperature; in contrast, aproduct comprising approximately 39 percent of the polyethylene glycol600 and approximately the same concentration of sodium nitrite andtriethanolamine showed no deposit formation even after several months ofstorage at atmospheric temperature. A polyglycol concentration of atleast 5 percent is necessary for the product to have good lubricatingproperties. Products with a polyglycol concentration below about 5weight percent are deficient in lubricating properties.

The alkali metal nitrite component of the lubricant composition of theinvention is preferably sodium nitrite because of its low cost but otheralkali metal nitrites such as potassium and lithium nitrite are alsoused. The lubricants of the invention are usually prepared with between7 and 15 weight percent alkali metal nitrite but 3,000,826 K I v y 3 a 4concentrations as high as 18 percent and as low as 3 y i following qcutting fluids 1n the afore percent may be employed. described rustlngtest:

In order to provide the desired rust protection it is necessary toemploy an aliphatic alkanol amine in conjunction with the inorganicmetal nitrite. The alkanol amine 5 is a secondary or tertiary alkanolamine of the general formula: RR'R"N wherein R is selected from thegroup consisting of hydrogen, an alkyl radical and a hydroxysubstitutedalkyl radical, R is selected from the group consisting of an alkylradical, a hydroxy-substituted alkyl radical or an amino-substitutedalkyl radical, and R is a hydroXy-substituted alkyl radical, said alkyl,hydroxy alkyl and amino alkyl radicals containing 1 to 8 carbon atomsand preferably 1 to 4 carbon atoms.

Examples of alkanol amines useful in the formulation of the transparentcutting fluids of the invention are triethanolamine, diethanolamine,tri(4-hydroxy-n-butyl) amine, di(2-hydroxy-nbutyl) amine,triisopropanolamine, diisopropanolamine, dimethyl ethanolamine,monoethyl ethanolamine, methyl (4hydroxy-n-butyl) amine, 2- 2Oamino-ethyl ethanolamine, amino-methyl ethanolamine and aminoethylisopropanolamine. Mixtures of secondary and tertiary alkanol amines suchas mixed isopropanolamines containing primary, secondary and tertiaryisopropanol amines are also usable in the formulation of the transparentcutting fluids of the invention. Particularly preferred alkanol aminesare triethanolamine, a mixture of diand triethanolaminm, triisopropanolamine, and aminoethyl ethanolamine. Exceptionally high rust protectionis obtained with these alkanol amines.

It is necessary for the alkauol amine to have the prescribed formulasince aryl-substituted alkanol amines such as phenyl ethanolamiue do notgive the desired rust protection.

The alkanol amine prescribed formula constitutes 2 to 15 weight percentof the lubricant composition. The usual concentration falls betweenapproximately 5 and 12 Weight percent but concentrations as high as 15Weight percent are employed in concentrates.

The alkanol amine has the dual function of providing anti-rustproperties and of improving lubricity. The alkanol amine impartsanti-rust properties in conjunction with the alkali metal nitrite andimparts lubricity in conjunction with the polyglycol of prescribedmolecular weight.

The outstanding anti-rust properties of the cutting fluids of thisinvention in comparison with other aqueous cutting fluids were shown ina rusting test which is specifically designed to evaluate the rustprotection afiorded by soluble oils and aqueous cutting fluids and whichinvolves the determination of what dilution of a soluble oil or cuttingfluid with synthetic hard water causes the rusting of cast iron. Theprocedure involves placing portions of solutions formed from the cuttingfluid in varying amounts of synthetic hard water on a polished cast ironplate 11" x 5 /2" x /2" which is cross-hatched into 162 equal squares.Drops of solutions ranging from a 10:1 dilution to a 90:1 dilution inincrements of 5 are placed on different squares of the polished castiron plate. The plate containing the various dilutions is allowed tostand overnight in an area where there is adequate ventilation, underwhich conditions the emulsion drops are evaporated in 1 to 2 hours. Thesquares are examined for signs of rust and the highest dilution showingno rust whatever is noted and reported as No Rust and the lowestdilution showing rust is noted and reported as the Rust dilution.

The synthetic hard water contains 125 ppm. hardness and is prepared bydissolving 2.77 g. of anhydrous calcium chloride and 5 gallons ofdistilled water and adjust- Oomp'osition A comprises:

20% polyethylene glycol 600 9% sodium nitrite 71% water Composition Bcomprises: a

10% polyethylene glycol 600 20% triethanolamine 70% water Composition Ccomprises:

20% polyethylene glycol 600 9% sodium nitrite 7% triethanolarnine 64%Water Composition D comprises:

20% polyethylene glycol 600 5% sodium nitrite 7% triethanolamine 68%Water Composition E comprises:

20% polyethylene glycol 600 11% sodium nitrite 7% triethanolamine 62%water a 1 Composition F comprises:

20% polyethylene glycol 600 9% sodium nitrite 11% triethanolamine 60%water Composition G comprises:

20% polyethylene glycol 600 9% sodium nitrite 5% triethauolamine 66%water Composition H comprises:

1% Pluronic L-44 0.5% disodium phosphate 0.5% sodium nitrite 98% waterComposition I comprises:

1% Pluronic L-62 0.5% disodium phosphate 0.5% sodium nitrite 45 98%Water Composition I comprises:

1% Pluronic L-64 0.5% disodium phosphate 0.5% sodium nitrite 98% waterComposition K comprises:

1% ammonium salt of sulfated nonylphenolethylene oxide (4 moles) adduct0.5% disodium phosphate 0.5% sodium nitrite 98% water TABLE I Rustingtest Composition The data in Table I clearly demonstrates the necessitying the pH to 6.5 to 7.5 by the addition of 10 percent of H or 10percent NaI-ICO In Table I there are shown the rust protection aiforded'of employing a combination of alkali metal nitrite and alkanol amine inorder to obtain a cutting fluid of high rust resistance andanti-staining properties. Compositions 1; A and B in whichtriethanolamine and sodium nitrite, respectively, were missing, gaverust at 10:1 dilution, whereas the products of the invention asrepresented by Compositions C through G all provided rust protection upto dilutions of 35 and above. Compositions C and F containingconcentrations of sodium nitrite and triethanolamine within thepreferred concentration range gave exceptionally high rust protectionsince rusting was only observed at dilutions of 75:1 and 85:1,respectively.

The data in Table I also establishes the superiority of the aqueouscutting fluids of this invention to the aqueous cutting fluids of theafore-identified Patent 2,692,859 wherein an alkali metal nitrite,inorganic phosphate combination is used as an anti-rust agent incombination with a water-soluble, non-ionic surface active agent such asan alkyl phenol-ethylene oxide adduct. Compositions H through K,representative of the cutting fluids of this patent, gave rust whendiluted with 10 parts of water, whereas the compositions of theinvention did not exhibit rust until diluted with 35 or more parts ofwater.

In an eflort to determine whether a higher degree of rust protection waspossessed by cutting fluids of the type described in US. 2,692,859containing higher concentrations of ingredients, two additional cuttingfluids were prepared. One contained 5 percent Pluronic L-62, 5 percentsodium nitrite, 5 percent disodium acid phosphate, and 85 percent water,and the other contained percent Pluronic L-62, 10 percent sodium nitriteand 10 percent disodium acid phosphate. Both of these products separatedinto two phases and products were too hazy to be considered transparentcutting fluids. Accordingly, neither product was subjected to therusting test since they evidently did not fulfill the requirements of atransparent cutting fluid.

In Table ii there are shown the rusting properties of aqueous cuttingfluids prepared with polyglycols of varying molecular weight and withother alkanol amines. The compositions whose anti-rust properties wereevaluated in the rusting test in Table H were the following:

Composition L20% polyethylene glycol 200, 9% sodium nitrite, 7%triethanolamine, 64% water. Composition M20% polyethylene glycol 400, 9%sodium nitrite, 7% triethanolamine, 64% water. Composition N-20%polyethylene glycol 1000, 9% sodium nitrite, 7% triethanolamine, 64%water. Composition O20% polyethylene glycol 600, 9% so- Rusting testComposition The data in Table H indicate that satisfactory products areobtained with polyethylene glycol 200 and 400 Whereas the use ofpolyethylene glycol 1000 in Composition N results in a non-transparent,hazy product. These data confirm the necessity of employing apolyethylene glycol 55. sparenttgohazy.

of an average molecular weight between 200 and 800 in order to producetransparent cutting fluids of the invention.

With respect to the alkanol amine component, the data in Table I1 provethe necessity of employing secondary or tertiary amines in which atleast one of the nitrogen substituents is an alkanol radical.Compositions O, P, Q,

wherein aminoethyl ethanolamine, mixed isopropanola- I mines anddimethyl ethanolamine, respectively, were used in place oftriethanolamine, were all transparent fluids of excellent anti-rustproperties. In contrast, Composition R employing phenyl ethanolamine inconjunction with sodium nitrite as an anti-rust agent possessed pooranti-rust properties as evidenced by the production of rust at 10:1dilution.

Transparent cutting fluids of the invention also possess othercharacteristics necessary for a highly effective transparent cuttingfluid. The product possesses heat stability and is very stable at lowtemperature. The polyglycol component imparts a low freezing point tothe cutting fluid of the invention.

Field evaluation of the metal cutting fluids of the invention hasconfirmed the excellent results obtained in the laboratory screeningtest. The use of the cutting fluid of the invention has resulted inexcellent tool life and has promoted cutting efliciency. At onelocation, Composition C comprising 20 percent polyethylene glycol 600, 9percent sodium nitrite, 7 percent triethanolamine and 64 percent waterwas evaluated as a lubricant for a Landis crankshaft grinder.Composition C out-performed a commercial soluble oil. Its performancewas deemed excellent by the operator from Whom the following observationwas obtained: Composition C cleaned up the grinder, gave satisfactoryfinishes, kept the gauges clean, helped speed up inspection bymaintaining a clean solution, and in general provided rust-free andcorrosionfree performance. At another location, Composition C wasevaluated in a Blanchard Cincinnati Filmatic blade sharpening machineand in a Schneider grinder with excellent results. In the opinion of theoperators, Composition C was the best grinding coolant they hadevaluated. It clearly out-performed commercial soluble oils and even inan :1 dilution no rust was obtained and the machines and work piecesremained stain-free. As a result of its excellent performance,Composition C is being used exclusively at this location for allgrinding operations.

Obviously, many modifications and variations of the invention ashereinbefore set forth may be made without departing from the spirit andscope thereof, and, therefore, only such limitations should be imposedas are indicated in the appended claims.

I claim:

1. A metal working lubricant composition consisting essentially of wateras the main component, 5 to 40 weight percent of a polyglycol selectedfrom a group consisting of polyethylene glycols, polypropylene glycols,and mixtures thereof having an average molecular weight between 200 and800, 3 to 18 weight percent alkali metal nitrite, and 2 to 15 weightpercent of an alkanol amine having the general formula: RR'RN wherein Ris selected from a group consisting of hydrogen, an alkyl radical and ahydroxy alkyl radical; R is selected from a group consisting of an alkylradical, a hydroxy alkyl radical and an amino alkyl radical; and R" is ahydroxy alkyl radical, said alkyl, hydroxy alkyl, and amino alkylradicals containing 1 to 4 carbon atoms.

2. A metal working lubricant composition according to claim 1 in whichthe polyglycol has an average molecular weight between 400 and 700 andconstitutes 15 to 35 weight percent of the composition.

3. A metal Working lubricant composition according to claim 1 containing7 to 15 weight percent alkali metal nitrite.

4. A metal working lubricant composition according to claim 1 containing5 to 12 weight percent alkanol amine.

5. A metal working lubricant composition consisting essentially of wateras the main component, 5 to 40 weight percent polyethylene glycol havingan average molecular weight between 200 and 800, 3 to 18 weight percentsodium nitrite and 2 to 15 Weight percent triethanolamine.

6. A metal Working lubricant composition according to claim 5 containing15 to 35 weight percent polyethylene glycol having an average molecularweight between 400 and 700, 7 to 15 weight percent sodium nitrite and 5to 12 weight percent triethanolamine.

7. A metal working lubricant composition consisting essentially of 20percent polyethylene glycol 600, 9 percent sodium nitrite and 7 percenttriethanolamine and the remainder being water.

8. A metal working lubricant composition consisting essentially of 20percent polyethylene glycol 600, 9 per- References Cited in the file ofthis patent UNITED STATES PATENTS 10 2,252,385 Orozco Aug. 12, 19412,328,727 Langer Sept. 7, 1943 2,692,859 Talley Oct. 26, 1954 2,825,693Beaubien et al. Mar. 4, 1958 OTHER REFERENCES Carbowax Compounds andPolyethylene Glycols," pub. of Carbide and Carbon Corp., N.Y., 1946,page 3.

Ucon Fluids and Lubricants, pub. of Carbide and Carbon Corp., N.Y.,1947, pages 3 and 13.

1. A METAL WORKING LUBRICANT COMPOSITION CONSISTING ESSENTIALLY OF WATERAS THE MAIN COMPONENT, 5 TO 40 WEIGHT PERCENT OF A POLYGLYCOL SELECTEDFROM A GROUP CONSISTING OF POLYETHYLENE GLYCOLS, POLYPROYLENE GLYCOLS,AND MIXTURES THEREOF HAVING AN AVERAGE MOLECULAR WEIGHT BETWEEN 200 AND800, 3 TO 18 WEIGHT PERCENT ALKALI METAL NITRITE, AND 2 TO 15 WEIGHTPERCENT OF AN ALKANOL AMINE HAVING THE GENERAL FORMULA: RR''R"N WHEREINR IS SELECTED FROM A GROUP CONSISTING OF HYDROGEN, AN ALKYL RADICAL ANDAN AMINO ALKYL RADICAL, R'' IS SELECTED FROM A GROUP CONSISTING OF ANALKYL RADICAL, A HYDROXY ALKYL RADICAL AND AN AMINO ALKYL RADICAL, ANDR" IS A HYDROXY ALKYL RADICAL, SAID ALKYL, HYDROXY ALKYL, AND AMINOALKYL RADICALS CONTAINING 1 TO 4 CARBON ATOMS.